In U.S. Pat. No. 4,714,937, various prior art ink delivery systems are described as well as some of the problems associated therewith. The patent describes a new system which is designed to overcome prior art problems. The new patented system comprises a toner bag, a print head, a bladder for delivering toner to the print head at a controlled pressure, a valve for controlling the flow of toner from the bag to bladder and separately from the bladder to the print head.